JP7177932B6 - Low viscosity UV curable formulations for 3D printing - Google Patents

Description

The present invention relates to additive manufacturing and, more particularly, to compositions for dispensing in additive manufacturing systems.

Additive manufacturing (AM), also known as solid freeform manufacturing or 3D printing, continuously dispenses raw materials (e.g., powders, liquids, suspensions, or molten solids) to form two-dimensional layers. Hence, it refers to a manufacturing process that builds up a three-dimensional object. In contrast, conventional machining techniques involve subtractive processes in which articles are cut from stock material (eg, wood, plastic, composites, or metal).

Polishing pads for chemical mechanical polishing are typically made by molding or casting a polyurethane material. In the case of molding, the polishing pads can be made one by one, for example by injection molding. For casting, a liquid precursor is cast and cured into a solid, which is then sliced into individual pad pieces. These pad pieces can then be machined to final thickness. Grooves can be machined into the polished surface or can be formed as part of the injection molding process.

Polishing pads can also be manufactured by 3D printing techniques. A liquid precursor material may be dispensed from a nozzle that moves over the support and cured to form a layer of the polishing pad.

In one aspect, a liquid precursor material for dispensing in an additive manufacturing process comprises a meth(acrylate) functional oligomer, a reactive diluent, a meth(acrylamide) monomer, and an N-vinyl containing monomer.

In another aspect, a method of manufacturing a polishing layer of a polishing pad includes sequentially depositing multiple sublayers of the polishing layer using a 3D printer. Each sublayer of the plurality of sublayers ejects a liquid precursor material from a nozzle, the precursor material comprising a meth(acrylate) functional oligomer, a reactive diluent, a meth(acrylamide) monomer, and N - Deposited by ejecting a liquid precursor material, including a vinyl-containing monomer, from a nozzle and curing the precursor material to form a solidified abrasive layer of the sublayer.

Potential benefits may include, but are not limited to, one or more of the following.

Precursor materials may have reduced viscosity, but may also have rapid cure, high modulus, and high ultimate tensile strength (UTS). Moreover, these properties can be achieved while maintaining low water absorption in the final cured part. In addition, higher loadings of high molecular weight (MW) oligomers may be added to allow for tougher layers (ie, layers with higher elongation to break while maintaining UTS). Adjusting the composition of the formulation to reduce the water absorption of UV curable formulations containing acrylamide or N-vinyl containing monomers to <10% of the original weight after immersion in room temperature water for 4 days. is possible. This is particularly desirable for parts made by inkjet-based 3D printing techniques.

The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the specification and drawings, and from the claims.

1 is a schematic cross-sectional side view of an exemplary additive manufacturing system; FIG. 1 is a table listing control UV-crosslinkable formulations. 1 is a table listing several formulations containing acrylamide and N-vinyl monomers. 1 is a table listing multiple 3D printed formulations. 5 is a table listing the mechanical properties of 3D printed specimens of the formulation of FIG. 4; 1 is a schematic cross-sectional side view of an exemplary polishing pad; FIG.

Similar reference symbols in the various drawings indicate similar elements.

Low viscosity formulations are highly desirable for many 3D printing techniques that use light-based curing, such as UV curing. This can be important for inkjet-based 3D printing techniques where the viscosity of the final formulation needs to be 10-20 cP at the jet temperature (60-90° C.). Conventionally, to achieve such low viscosities, most (~70-80%) of the formulation is a low viscosity reactive diluent, and only 20-25% of the formulation has the required mechanical properties. to the final layer. Thus, in most cases, the final UV-cured layer obtained by inkjet-based 3D techniques is very brittle and hard, in contrast to the more robust materials that can be obtained by sequential polymerization techniques.

Most reactive diluents used in UV curable layers are combinations of acrylate and methacrylate monomers with mono-, di-, tri-, or tetra-functional reactive (meth)acrylate groups. One such commonly used acrylate monomer is isobornyl acrylate, which has an RT viscosity of ˜8 cP and a Tg of ˜90C. Other low viscosity methacrylate monomers such as cyclohexyl methacrylate and methyl methacrylate are also used as reactive diluents. However, formulations based on these monomers are either very slow to cure or require very high doses of radiation to complete cure due to the slow reactivity of the methacrylate groups. Therefore, it is impractical to use large amounts of such monomers in formulations.

However, formulations containing acrylamide and N-vinyl containing monomers such as N,N dimethylacrylamide, N,N diethylacrylamide and N-vinylpyrrolidone can address these problems.

FIG. 1 is a simplified diagram of an exemplary system 10 for manufacturing parts, such as polishing pads, using a 3D printing process. System 10 includes a support 20 on which components are manufactured, and a droplet ejection printhead 30 , which includes one or more nozzles 32 . Droplets 34 of liquid precursor material may be ejected from one or more nozzles 32 . Droplet ejection printers may be similar to inkjet printers, but use precursor materials rather than inks. The printhead 30 and nozzles 32 translate across the support 20 (as indicated by arrow A). For example, the printhead 30 is supported on a linear track 36 and moved along the track 36 by a linear actuator 38, such as a screw drive motor. Alternatively, the printhead 30 can be stationary and the support 20 moved horizontally by a motor.

In some implementations, support 20 may be moved by vertical actuator 22 . For example, after each layer is deposited, support 20 may be lowered a distance equal to the thickness of the layer just deposited. Alternatively or additionally, printhead 30 may be moved vertically, for example to provide some or all of the vertical displacement. This can ensure a uniform distance between the nozzle 32 and the surface on which the droplets 34 are deposited, thereby improving manufacturing uniformity and simplifying control electronics. can do.

Support 20 may be a rigid base or may be a flexible membrane, such as a layer of polytetrafluoroethylene (PTFE). If the support 20 is a membrane, the support 20 may form part of the article. For example, support 20 may form a backing layer or a layer between the backing layer and the polishing layer of the polishing pad. Alternatively, the component can be removed from support 20 .

Although FIG. 1 shows a single nozzle 32, in practice printhead 30 may include a linear array of independently controllable nozzles. The nozzles may extend in a direction parallel to the support surface and oblique or perpendicular to the direction of motion of the printhead 30 . The array of nozzles 32 can span the width of the build area of the support 20 .

System 10 also includes an energy source 40 for emitting radiation 42 to solidify, eg, cure liquid precursor material 34 . For example, energy source 40 may include one or more UV lamps. For example, energy source 40 may include a linear array of LEDs, such as UV light emitting diodes. The linear array of LEDs can span the width of the build area of the support 20 . The energy source 40 may also translate the entire support 20 , for example in the same direction as the printhead 30 . For example, printhead 30 and energy source 40 may be supported on a common frame that is moved as a unit, or printhead 30 and energy source 40 may be independently movable along the same or different tracks. .

Coagulation can be achieved by polymerization. For example, the layer of pad precursor material 50 can be a monomer, and the monomer can be polymerized in situ by UV curing. The pad precursor material may be cured substantially immediately after deposition, although all layers 50 of pad precursor material may be cured simultaneously after all layers 50 are deposited.

In the manufacturing process, thin layers of material are gradually deposited and solidified. For example, droplets 34 of precursor material are ejected from nozzle 32 to form layer 50 . At the deposited first layer 50a, the nozzle 34 can jet onto the support 20. As shown in FIG. In the subsequently deposited layer 50b, the nozzle 34 may discharge onto the material 56 that has already solidified. After each layer 50 solidifies, new layers are deposited over the previous deposited layers until a complete three-dimensional part, eg a polishing pad, is manufactured. Each layer 50 is less than 50% (eg, less than 10%, such as less than 5%, such as less than 1%) of the total thickness of the part.

Computer 60 so that each layer is applied in a pattern stored as data in a non-transitory computer readable medium, e.g., a 3D rendering computer program, on computer 60 as print head 30 moves relative to the substrate. may control droplet ejection from various nozzles 34 . The computer 60 can control various actuators, for example to control the translation speed of the printhead 30 and/or the energy source 40, for example to control the intensity of the radiation 42 and thereby control the curing speed. The energy source 40 can be controlled to do so, and the vertical actuators of the support 20 can be controlled.

The liquid precursor material of droplets 34 can be a formulation comprising acrylamide and N-vinyl containing monomers such as, for example, N,N dimethylacrylamide, N,N diethylacrylamide and/or N-vinylpyrrolidone. Such formulations may have low viscosities suitable for forming UV curable layers in additive manufacturing, such as inkjet-based 3D printing. However, the formulation can also be used for other 3D printing techniques, such as stereolithography (SLA) or digital light processing (DLP). Additionally, the formulations may be applicable to other uses, such as coatings on other articles, such as protective coatings. Potential applications for these 3D printed parts include functional and prototyping applications, as well as manufacturing polishing pads for chemical mechanical planarization (CMP) for semiconductor manufacturing.

UV curable monomers such as acrylamide and N-vinyl monomers have previously been used in UV curable formulations other than 3D printing of superabsorbent systems such as hydrogels due to the high water solubility of these monomers. Surprisingly, it was discovered that such formulations can have reduced viscosity, but can also have rapid cure, high modulus, and high ultimate tensile strength (UTS). Moreover, these properties can be achieved while maintaining low moisture absorption in the final cured part. In addition, higher loadings of high molecular weight (MW) oligomers may be added to allow for tougher layers (ie, layers with higher elongation to break while maintaining UTS). Adjusting the composition of the formulation to reduce the moisture absorption of UV curable formulations containing acrylamide or N-vinyl containing monomers to <10% of the original weight after immersion in room temperature water for 4 days. is possible. This is particularly desirable for parts made by inkjet-based 3D printing techniques.

The formulation includes a meth(acrylate) functional oligomer, a reactive diluent, a meth(acrylamide) monomer, and an N-vinyl containing monomer. Reactive diluents can be aliphatic, cycloaliphatic, heterocyclic, aromatic, linear or branched meta(acrylate) monomers. N-vinyl containing monomers may include N,N dimethylacrylamide, N,N diethylacrylamide and/or N-vinylpyrrolidone. The formulation may contain photoinitiators, photosensitizers, and/or oxygen scavengers to improve performance. However, the chemically reactive portion of the formulation may only comprise, eg consist of, meth(acrylate) functional oligomers, reactive diluents, meth(acrylamide) monomers, N-vinyl containing monomers.

FIG. 2 is a table listing control UV crosslinkable formulations using EB270 oligomer (aliphatic urethane acrylate) and BR744BT oligomer (aliphatic polyester urethane acrylate). Monomer 1 is isobornyl acrylate (IBOA). Monomer 3 is a low viscosity trimethylolpropane triacrylate (TMPTA) available from Sartomer Americas under the tradename "SR 351 LV". The photoinitiator (PI) is Omnirad ^™ 819 available from IGM Resins USA, Inc., Charlotte, North Carolina, USA. Weight percentages (%) of oligomer, monomer 1, monomer 3, and photoinitiator are indicated. In the tables of Figures 2 to 5, viscosity is given in centipoise (cP) at 70°C. Ultimate Tensile Strength (UTS) is given in millipascals (MPa). % EI is the percent elongation at break. The storage modulus is given at 30°C (E30), 60°C (E60), and 90°C (E90).

As shown in the table of Figure 2, for two of the representative oligomers, the viscosities of the two model formulations were too high and the mechanical properties were too high for the production of functional parts by rapid prototyping or 3D printing. is still insufficient.

FIG. 3 is a table listing several formulations containing acrylamide and N-vinyl monomers having lower viscosities and better mechanical properties than the control formulation in the table of FIG. Monomeric DEAA is N,N-diethylacrylamide. Monomeric DMAA is N,N-dimethylacrylamide. Monomer NVP is N-vinylpyrrolidone. Weight percentages (%) of oligomer, Monomer 1, Monomer 2, Monomer 3, Monomer 4, and photoinitiator (PI) are shown in brackets.

For 3D printing techniques such as DLP, SLA, and Polyjet techniques, low viscosity formulations that enable rapid prototyping or production of functional parts are highly desirable. Low viscosity formulations are easier to handle and provide higher resolution when printed. To achieve such low viscosities, the ink composition comprises mostly, for example, at least about 50%, such as 70-80%, low viscosity liquids such as meth(acrylate) monomers, meth(acrylamide). monomers, and N-vinyl containing monomers. About 20-30%, such as 20-25%, of the composition may be high viscosity oligomers that provide the required mechanical properties to the final cured layer.

FIG. 4 is a table listing multiple formulations (#10-14) that were 3D printed using a Stratasys Connex 500 printer to form Type IV and Type V dogbone and DMA coupon samples. After printing, the 3D printed samples were cured at 90° C. for 1 hour, at which point the samples were cooled to room temperature. All samples were characterized after the samples were placed at room temperature for 24 hours. Samples were characterized for UTS, % elongation at break, storage modulus at 30° C. and 90° C., and water absorption after 96 hours of immersion testing at room temperature. Preferred values for 3D printed samples are 25-35 MPa, 20-75%, ~1 GPa-1.5 GPa, 35-200 MPa, and >10% for UTS, % elongation at break, E30, E90, and water absorption, respectively. is.

In Table 4, the weight percentages (%) of oligomer, Monomer 1, Monomer 2, Monomer 3, Monomer 4, and photoinitiator (PI) are shown in brackets. Monomer SR 420 is a very low viscosity monofunctional acrylic monomer from Sartomer Americas. Monomer TMCHA is 3,3,5-trimethylcyclohexyl methacrylate. Monomer 1.4 BDDA is 1,4-butanediol diacrylate.

FIG. 5 is a table listing the mechanical properties of 3D printed specimens of Formulations #11-#14 of the table of FIG.

Formulations with low viscosity and containing acrylamide and N-vinyl monomers are particularly desirable for additive manufacturing. One such application of formulations using the PolyJet 3D printing technique is to make advanced chemical vapor polishing (CMP) pads with higher elongation and UTS. The viscosity range of the formulation at jet temperature may be between 10 cP and 25 cP, such as between 12 cp and 20 cP, such as between 13 cp and 16 cP. The jet temperature of such formulations may be between 50°C and 100°C, such as between 55°C and 80°C, such as between 60°C and 70°C.

6A and 6B illustrate a polishing pad 100 that can be produced by additive manufacturing using the precursor material formulations discussed above and in Tables 3 and 4. FIG. As shown in FIG. 6A, polishing pad 100 can be a single layer pad consisting of a polishing layer 102 manufactured by additive manufacturing using the precursor materials described above. Alternatively, as shown in FIG. 6B, polishing pad 100 can be a multi-layer pad including polishing layer 102 and at least one backing layer 104 .

Polishing layer 102 may be an inert material in the polishing process. The polishing layer 102 may have a hardness of about 40-80, such as 50-65, on the Shore D scale. In some implementations, polishing layer 102 can be a layer of homogeneous composition. In some implementations, the polishing layer 102 includes pores, eg, small voids. The pores may be 50-100 microns wide.

The polishing layer 102 may have a thickness D1 of 80 mils or less, such as 50 mils or less, such as 25 mils or less. Because the conditioning process tends to wear away the cover layer, the thickness of polishing layer 102 may be selected to provide polishing pad 100 with a useful life of, for example, 3000 polishing and conditioning cycles.

On a microscopic scale, the polishing surface 106 of the polishing layer 102 can have a rough textured surface, eg, 2-4 microns rms. For example, polishing layer 102 can be subjected to a grinding or conditioning process to produce a rough surface texture. Additionally, 3D printing can provide small uniform features, for example, up to 200 microns.

The polishing surface 106 can be rough on a microscopic scale, but on the macroscopic scale of the polishing pad itself, the polishing layer 106 can have good thickness uniformity (this uniformity is measured by the thickness of the polishing surface 106 relative to the bottom surface of the polishing layer). and does not include any gross grooves or through-holes intentionally formed in the polishing layer). For example, the thickness non-uniformity can be less than 1 mil.

In some cases, at least a portion of polishing surface 106 may include a plurality of grooves 108 formed therein for carrying slurry. Grooves 108 can be formed by simply not ejecting precursor material at locations corresponding to the grooves. The grooves 108 can be of almost any pattern, such as concentric circles, straight lines, cross-hatching, spirals, and the like. Assuming grooves 108 , the polishing surface 106 , ie, the plateau between grooves 108 , may amount to about 25-90% of the total horizontal surface area of polishing pad 100 . Thus, grooves 108 may occupy 10-75% of the total horizontal surface area of polishing pad 18 . The plateaus between grooves 26 may have a lateral width of about 0.1-2.5 mm.

In some implementations, grooves 108 may extend completely through polishing layer 102 , for example when backing layer 104 is present. In some implementations, grooves 108 may extend through approximately 20-80% (eg, 40%) of the thickness of polishing layer 102 . The depth D2 of groove 108 may be between 0.25 and 1 mm. For example, in a polishing pad 100 having a polishing layer 102 that is 50 mils thick, grooves 108 can be about 20 mils deep D2.

Backing layer 104 may be softer and more compressible than polishing layer 102 . The backing layer 104 may have a hardness of 80 or less on the Shore A scale, such as about 60 Shore A hardness. The backing layer 104 may be thicker, thinner, or the same thickness as the polishing layer 102 .

For example, the backing layer may be an open-cell or closed-cell foam, such as polyurethane or polysilicon, with voids that cause the cells to collapse under pressure, compressing the backing layer. Suitable backing layer materials are PORON 4701-30 from Rogers, Inc. of Rogers, Connecticut, or SUBA-IV from Rohm & Haas. The hardness of the backing layer can be adjusted by selecting the layer material and porosity.

In some implementations, the backing layer 104 may also be manufactured by a 3D printing process. For example, backing layer 104 and polishing layer 102 can be manufactured by additive manufacturing system 10 in one continuous process. The backing layer 104 may be given a different hardness than the polishing layer 102 by using different precursor materials and/or by using different amounts of curing, eg, different UV radiation intensities.

In other implementations, the backing layer 104 is manufactured by conventional processes and then secured to the polishing layer 102 . For example, abrasive layer 102 may be secured to backing layer 104 by a thin adhesive layer, such as a pressure sensitive adhesive.

A number of implementations have been described. Nevertheless, it will be understood that various modifications can be made without departing from the spirit and scope of the invention.

The thickness of each layer of layers and the size of each of the voxels may vary from implementation to implementation. In some implementations, each voxel is, for example, 10 μm to 50 μm (10 μm to 30 μm, 20 μm to 40 μm, 30 μm to 50 μm, approximately 20 μm, approximately 30 μm, or approximately 50 μm, etc.) when dispensed onto support 20. ). Each layer may have a predetermined thickness. The thickness is for example 0.10 μm to 125 μm (for example 0.1 μm to 1 μm, 1 μm to 10 μm, 10 μm to 20 μm, 10 μm to 40 μm, 40 μm to 80 μm, 80 μm to 125 μm, approximately 15 μm, approximately 25 μm, approximately 60 μm, or approximately 100 μm).

The polishing pad can be a circular or some other shaped pad.

The energy source may include multiple light sources with different wavelength ranges. For example, the energy source may include two rows of UV light sources, the two rows having different wavelength bands.

Although the apparatus has been described in connection with the manufacture of polishing pads, the apparatus may also be adapted to manufacture other articles by additive manufacturing.

Accordingly, other implementations are also within the scope of the following claims.

Claims (15)

A liquid precursor in an additive manufacturing process, comprising:
a meta(acrylate) functional oligomer;
a reactive diluent;
a meta(acrylamide) monomer;
N,N diethylacrylamide monomer and/or N,N dimethylacrylamide monomer ;
including
A liquid precursor wherein the reactive diluent, meta(acrylamide) monomer, N,N diethylacrylamide monomer or N,N dimethylacrylamide monomer or both are 70-80% of the liquid precursor . 2. The liquid precursor of Claim 1, wherein the reactive diluent comprises a meth(acrylate) monomer. 3. The liquid precursor of claim 2, wherein the meth(acrylate) monomers comprise aliphatic, cycloaliphatic, heterocyclic, aromatic, linear and/or branched meth(acrylate) monomers. 2. The liquid precursor of claim 1, wherein the liquid precursor does not contain N -vinylpyrrolidone. Liquid precursor according to claim 1, wherein the oligomers in the liquid precursor are only meth(acrylate) functional oligomers, the meth(acrylate) functional oligomers accounting for 20-30% of the liquid precursor. 6. The liquid precursor of claim 5, wherein the meth(acrylate) functional oligomer comprises 20-25% of the liquid precursor. 2. The liquid precursor of Claim 1, comprising a photoinitiator, a photosensitizer, and/or an oxygen scavenger. The liquid precursor comprises a meth(acrylate) functional oligomer, a reactive diluent, a meth(acrylamide) monomer, and an N-vinyl-containing monomer, and optionally a photoinitiator, photosensitizer, and/or oxygen scavenger. 2. The liquid precursor of claim 1, consisting of one or more of the agents. A method of manufacturing a polishing layer of a polishing pad, comprising:
sequentially depositing a plurality of sublayers of the polishing layer using a 3D printer, each sublayer of the plurality of sublayers comprising:
Dispensing a liquid precursor material from a nozzle, wherein the liquid precursor material comprises a meth(acrylate) functional oligomer , a reactive diluent , a meth(acrylamide) monomer , a N,N diethylacrylamide monomer or N ,N dimethylacrylamide monomer or both , wherein the reactive diluent, the meta(acrylamide) monomer, and the N,N diethylacrylamide monomer and/or the N,N dimethylacrylamide monomer form the liquid precursor material. ejecting a liquid precursor material from a nozzle that is 70-80% ; and
Curing the liquid precursor material to solidify the liquid precursor material to form a solidified abrasive layer material of the sublayer, wherein the water absorption of the solidified abrasive layer material is reduced to four days in room temperature water. deposited by forming a sublayer of solidified abrasive layer material that is less than 10% of its original weight after soaking ;
sequentially depositing multiple sublayers of the polishing layer using a 3D printer;
Method. 10. The method of claim 9 , wherein the oligomers in the liquid precursor material are only meth(acrylate) functional oligomers and the thickness of each sublayer of the plurality of sublayers is less than 50% of the total thickness of the polishing layer. Method. The reactive diluent is a meth(acrylate) monomer, and the chemically reactive portions of the liquid precursor are a meth(acrylate) functional oligomer, a meth(acrylate) monomer, a meth(acrylamide) monomer, N ,N dimethylacrylamide monomer and/or N,N diethylacrylamide monomer, wherein the thickness of each sublayer of the plurality of sublayers is less than 1% of the total thickness of the polishing layer. the method of. 10. The method of claim 9, wherein the reactive diluent comprises a meth(acrylate) monomer. 10. The method of claim 9, wherein the liquid precursor material does not contain N-vinylpyrrolidone. 10. The method of claim 9, wherein the meth(acrylate) functional oligomer comprises 20-30% of the liquid precursor material . The liquid precursor material comprises a meth(acrylate) functional oligomer, a reactive diluent, a meth(acrylamide) monomer, and N,N diethylacrylamide and/or N,N dimethylacrylamide monomers , and optionally photoinitiation. 10. The method of claim 9 , comprising one or more of an agent, a photosensitizer, and/or an oxygen scavenger.

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